/*

** 2005 May 23 

**

** The author disclaims copyright to this source code.  In place of

** a legal notice, here is a blessing:

**

**    May you do good and not evil.

**    May you find forgiveness for yourself and forgive others.

**    May you share freely, never taking more than you give.

**

*************************************************************************

**

** This file contains functions used to access the internal hash tables

** of user defined functions and collation sequences.

**

** $Id: callback.c,v 1.32 2008/10/10 17:41:29 drh Exp $

*/

#include "sqliteInt.h"

/*

** Invoke the 'collation needed' callback to request a collation sequence

** in the database text encoding of name zName, length nName.

** If the collation sequence

*/

static void callCollNeeded(sqlite3 *db, const char *zName, int nName){

  assert( !db->xCollNeeded || !db->xCollNeeded16 );

  if( nName<0 ) nName = sqlite3Strlen(db, zName);

  if( db->xCollNeeded ){

    char *zExternal = sqlite3DbStrNDup(db, zName, nName);

    if( !zExternal ) return;

    db->xCollNeeded(db->pCollNeededArg, db, (int)ENC(db), zExternal);

    sqlite3DbFree(db, zExternal);

  }

#ifndef SQLITE_OMIT_UTF16

  if( db->xCollNeeded16 ){

    char const *zExternal;

    sqlite3_value *pTmp = sqlite3ValueNew(db);

    sqlite3ValueSetStr(pTmp, nName, zName, SQLITE_UTF8, SQLITE_STATIC);

    zExternal = sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);

    if( zExternal ){

      db->xCollNeeded16(db->pCollNeededArg, db, (int)ENC(db), zExternal);

    }

    sqlite3ValueFree(pTmp);

  }

#endif

}

/*

** This routine is called if the collation factory fails to deliver a

** collation function in the best encoding but there may be other versions

** of this collation function (for other text encodings) available. Use one

** of these instead if they exist. Avoid a UTF-8 <-> UTF-16 conversion if

** possible.

*/

static int synthCollSeq(sqlite3 *db, CollSeq *pColl){

  CollSeq *pColl2;

  char *z = pColl->zName;

  int n = strlen(z);

  int i;

  static const u8 aEnc[] = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };

  for(i=0; i<3; i++){

    pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, n, 0);

    if( pColl2->xCmp!=0 ){

      memcpy(pColl, pColl2, sizeof(CollSeq));

      pColl->xDel = 0;         /* Do not copy the destructor */

      return SQLITE_OK;

    }

  }

  return SQLITE_ERROR;

}

/*

** This function is responsible for invoking the collation factory callback

** or substituting a collation sequence of a different encoding when the

** requested collation sequence is not available in the database native

** encoding.

** 

** If it is not NULL, then pColl must point to the database native encoding 

** collation sequence with name zName, length nName.

**

** The return value is either the collation sequence to be used in database

** db for collation type name zName, length nName, or NULL, if no collation

** sequence can be found.

*/

CollSeq *sqlite3GetCollSeq(

  sqlite3* db, 

  CollSeq *pColl, 

  const char *zName, 

  int nName

){

  CollSeq *p;

  p = pColl;

  if( !p ){

    p = sqlite3FindCollSeq(db, ENC(db), zName, nName, 0);

  }

  if( !p || !p->xCmp ){

    /* No collation sequence of this type for this encoding is registered.

    ** Call the collation factory to see if it can supply us with one.

    */

    callCollNeeded(db, zName, nName);

    p = sqlite3FindCollSeq(db, ENC(db), zName, nName, 0);

  }

  if( p && !p->xCmp && synthCollSeq(db, p) ){

    p = 0;

  }

  assert( !p || p->xCmp );

  return p;

}

/*

** This routine is called on a collation sequence before it is used to

** check that it is defined. An undefined collation sequence exists when

** a database is loaded that contains references to collation sequences

** that have not been defined by sqlite3_create_collation() etc.

**

** If required, this routine calls the 'collation needed' callback to

** request a definition of the collating sequence. If this doesn't work, 

** an equivalent collating sequence that uses a text encoding different

** from the main database is substituted, if one is available.

*/

int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){

  if( pColl ){

    const char *zName = pColl->zName;

    CollSeq *p = sqlite3GetCollSeq(pParse->db, pColl, zName, -1);

    if( !p ){

      if( pParse->nErr==0 ){

        sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);

      }

      pParse->nErr++;

      return SQLITE_ERROR;

    }

    assert( p==pColl );

  }

  return SQLITE_OK;

}

/*

** Locate and return an entry from the db.aCollSeq hash table. If the entry

** specified by zName and nName is not found and parameter 'create' is

** true, then create a new entry. Otherwise return NULL.

**

** Each pointer stored in the sqlite3.aCollSeq hash table contains an

** array of three CollSeq structures. The first is the collation sequence

** prefferred for UTF-8, the second UTF-16le, and the third UTF-16be.

**

** Stored immediately after the three collation sequences is a copy of

** the collation sequence name. A pointer to this string is stored in

** each collation sequence structure.

*/

static CollSeq *findCollSeqEntry(

  sqlite3 *db,

  const char *zName,

  int nName,

  int create

){

  CollSeq *pColl;

  if( nName<0 ) nName = sqlite3Strlen(db, zName);

  pColl = sqlite3HashFind(&db->aCollSeq, zName, nName);

  if( 0==pColl && create ){

    pColl = sqlite3DbMallocZero(db, 3*sizeof(*pColl) + nName + 1 );

    if( pColl ){

      CollSeq *pDel = 0;

      pColl[0].zName = (char*)&pColl[3];

      pColl[0].enc = SQLITE_UTF8;

      pColl[1].zName = (char*)&pColl[3];

      pColl[1].enc = SQLITE_UTF16LE;

      pColl[2].zName = (char*)&pColl[3];

      pColl[2].enc = SQLITE_UTF16BE;

      memcpy(pColl[0].zName, zName, nName);

      pColl[0].zName[nName] = 0;

      pDel = sqlite3HashInsert(&db->aCollSeq, pColl[0].zName, nName, pColl);

      /* If a malloc() failure occured in sqlite3HashInsert(), it will 

      ** return the pColl pointer to be deleted (because it wasn't added

      ** to the hash table).

      */

      assert( pDel==0 || pDel==pColl );

      if( pDel!=0 ){

        db->mallocFailed = 1;

        sqlite3DbFree(db, pDel);

        pColl = 0;

      }

    }

  }

  return pColl;

}

/*

** Parameter zName points to a UTF-8 encoded string nName bytes long.

** Return the CollSeq* pointer for the collation sequence named zName

** for the encoding 'enc' from the database 'db'.

**

** If the entry specified is not found and 'create' is true, then create a

** new entry.  Otherwise return NULL.

**

** A separate function sqlite3LocateCollSeq() is a wrapper around

** this routine.  sqlite3LocateCollSeq() invokes the collation factory

** if necessary and generates an error message if the collating sequence

** cannot be found.

*/

CollSeq *sqlite3FindCollSeq(

  sqlite3 *db,

  u8 enc,

  const char *zName,

  int nName,

  int create

){

  CollSeq *pColl;

  if( zName ){

    pColl = findCollSeqEntry(db, zName, nName, create);

  }else{

    pColl = db->pDfltColl;

  }

  assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );

  assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );

  if( pColl ) pColl += enc-1;

  return pColl;

}

/* During the search for the best function definition, this procedure

** is called to test how well the function passed as the first argument

** matches the request for a function with nArg arguments in a system

** that uses encoding enc. The value returned indicates how well the

** request is matched. A higher value indicates a better match.

**

** The returned value is always between 1 and 6, as follows:

**

** 1: A variable arguments function that prefers UTF-8 when a UTF-16

**    encoding is requested, or vice versa.

** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is

**    requested, or vice versa.

** 3: A variable arguments function using the same text encoding.

** 4: A function with the exact number of arguments requested that

**    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.

** 5: A function with the exact number of arguments requested that

**    prefers UTF-16LE when UTF-16BE is requested, or vice versa.

** 6: An exact match.

**

*/

static int matchQuality(FuncDef *p, int nArg, u8 enc){

  int match = 0;

  if( p->nArg==-1 || p->nArg==nArg || nArg==-1 ){

    match = 1;

    if( p->nArg==nArg || nArg==-1 ){

      match = 4;

    }

    if( enc==p->iPrefEnc ){

      match += 2;

    }

    else if( (enc==SQLITE_UTF16LE && p->iPrefEnc==SQLITE_UTF16BE) ||

             (enc==SQLITE_UTF16BE && p->iPrefEnc==SQLITE_UTF16LE) ){

      match += 1;

    }

  }

  return match;

}

/*

** Search a FuncDefHash for a function with the given name.  Return

** a pointer to the matching FuncDef if found, or 0 if there is no match.

*/

static FuncDef *functionSearch(

  FuncDefHash *pHash,  /* Hash table to search */

  int h,               /* Hash of the name */

  const char *zFunc,   /* Name of function */

  int nFunc            /* Number of bytes in zFunc */

){

  FuncDef *p;

  for(p=pHash->a[h]; p; p=p->pHash){

    if( sqlite3StrNICmp(p->zName, zFunc, nFunc)==0 && p->zName[nFunc]==0 ){

      return p;

    }

  }

  return 0;

}

/*

** Insert a new FuncDef into a FuncDefHash hash table.

*/

void sqlite3FuncDefInsert(

  FuncDefHash *pHash,  /* The hash table into which to insert */

  FuncDef *pDef        /* The function definition to insert */

){

  FuncDef *pOther;

  int nName = strlen(pDef->zName);

  u8 c1 = (u8)pDef->zName[0];

  int h = (sqlite3UpperToLower[c1] + nName) % ArraySize(pHash->a);

  pOther = functionSearch(pHash, h, pDef->zName, nName);

  if( pOther ){

    pDef->pNext = pOther->pNext;

    pOther->pNext = pDef;

  }else{

    pDef->pNext = 0;

    pDef->pHash = pHash->a[h];

    pHash->a[h] = pDef;

  }

}

/*

** Locate a user function given a name, a number of arguments and a flag

** indicating whether the function prefers UTF-16 over UTF-8.  Return a

** pointer to the FuncDef structure that defines that function, or return

** NULL if the function does not exist.

**

** If the createFlag argument is true, then a new (blank) FuncDef

** structure is created and liked into the "db" structure if a

** no matching function previously existed.  When createFlag is true

** and the nArg parameter is -1, then only a function that accepts

** any number of arguments will be returned.

**

** If createFlag is false and nArg is -1, then the first valid

** function found is returned.  A function is valid if either xFunc

** or xStep is non-zero.

**

** If createFlag is false, then a function with the required name and

** number of arguments may be returned even if the eTextRep flag does not

** match that requested.

*/

FuncDef *sqlite3FindFunction(

  sqlite3 *db,       /* An open database */

  const char *zName, /* Name of the function.  Not null-terminated */

  int nName,         /* Number of characters in the name */

  int nArg,          /* Number of arguments.  -1 means any number */

  u8 enc,            /* Preferred text encoding */

  int createFlag     /* Create new entry if true and does not otherwise exist */

){

  FuncDef *p;         /* Iterator variable */

  FuncDef *pBest = 0; /* Best match found so far */

  int bestScore = 0;  /* Score of best match */

  int h;              /* Hash value */

  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );

  if( nArg<-1 ) nArg = -1;

  h = (sqlite3UpperToLower[(u8)zName[0]] + nName) % ArraySize(db->aFunc.a);

  /* First search for a match amongst the application-defined functions.

  */

  p = functionSearch(&db->aFunc, h, zName, nName);

  while( p ){

    int score = matchQuality(p, nArg, enc);

    if( score>bestScore ){

      pBest = p;

      bestScore = score;

    }

    p = p->pNext;

  }

  /* If no match is found, search the built-in functions.

  **

  ** Except, if createFlag is true, that means that we are trying to

  ** install a new function.  Whatever FuncDef structure is returned will

  ** have fields overwritten with new information appropriate for the

  ** new function.  But the FuncDefs for built-in functions are read-only.

  ** So we must not search for built-ins when creating a new function.

  */ 

  if( !createFlag && !pBest ){

    FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);

    p = functionSearch(pHash, h, zName, nName);

    while( p ){

      int score = matchQuality(p, nArg, enc);

      if( score>bestScore ){

        pBest = p;

        bestScore = score;

      }

      p = p->pNext;

    }

  }

  /* If the createFlag parameter is true and the search did not reveal an

  ** exact match for the name, number of arguments and encoding, then add a

  ** new entry to the hash table and return it.

  */

  if( createFlag && (bestScore<6 || pBest->nArg!=nArg) && 

      (pBest = sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){

    pBest->zName = (char *)&pBest[1];

    pBest->nArg = nArg;

    pBest->iPrefEnc = enc;

    memcpy(pBest->zName, zName, nName);

    pBest->zName[nName] = 0;

    sqlite3FuncDefInsert(&db->aFunc, pBest);

  }

  if( pBest && (pBest->xStep || pBest->xFunc || createFlag) ){

    return pBest;

  }

  return 0;

}

/*

** Free all resources held by the schema structure. The void* argument points

** at a Schema struct. This function does not call sqlite3DbFree(db, ) on the 

** pointer itself, it just cleans up subsiduary resources (i.e. the contents

** of the schema hash tables).

**

** The Schema.cache_size variable is not cleared.

*/

void sqlite3SchemaFree(void *p){

  Hash temp1;

  Hash temp2;

  HashElem *pElem;

  Schema *pSchema = (Schema *)p;

  temp1 = pSchema->tblHash;

  temp2 = pSchema->trigHash;

  sqlite3HashInit(&pSchema->trigHash, 0);

  sqlite3HashClear(&pSchema->aFKey);

  sqlite3HashClear(&pSchema->idxHash);

  for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){

    sqlite3DeleteTrigger(0, (Trigger*)sqliteHashData(pElem));

  }

  sqlite3HashClear(&temp2);

  sqlite3HashInit(&pSchema->tblHash, 0);

  for(pElem=sqliteHashFirst(&temp1); pElem; pElem=sqliteHashNext(pElem)){

    Table *pTab = sqliteHashData(pElem);

    sqlite3DeleteTable(pTab);

  }

  sqlite3HashClear(&temp1);

  pSchema->pSeqTab = 0;

  pSchema->flags &= ~DB_SchemaLoaded;

}

/*

** Find and return the schema associated with a BTree.  Create

** a new one if necessary.

*/

Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){

  Schema * p;

  if( pBt ){

    p = (Schema *)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaFree);

  }else{

    p = (Schema *)sqlite3MallocZero(sizeof(Schema));

  }

  if( !p ){

    db->mallocFailed = 1;

  }else if ( 0==p->file_format ){

    sqlite3HashInit(&p->tblHash, 0);

    sqlite3HashInit(&p->idxHash, 0);

    sqlite3HashInit(&p->trigHash, 0);

    sqlite3HashInit(&p->aFKey, 1);

    p->enc = SQLITE_UTF8;

  }

  return p;

}